Rhus coriaria Linn Extract as a Natural Inhibitor of Influenza A Virus Replication In Vitro

Influenza A viruses remain a major public health threat due to their high mutation rates, antigenic variability, and the emergence of resistance to current antivirals, underscoring the need for novel therapeutic options. Natural compounds rich in polyphenols and flavonoids have attracted increasing attention as potential broad-spectrum antiviral agents. In this study, the activity of <i>Rhus coriaria</i> L. water extract against Influenza A virus in BEAS-2B human bronchial epithelial cells was investigated. Cell viability assay identified non-cytotoxic concentrations, up to 0.1 mg/mL, which were used in infection experiments. Viral replication was assessed at multiple levels by quantitative real-time PCR, western blotting, immunofluorescence and tissue culture infectious dose 50% (TCID₅₀). Treatment with <i>R. coriaria</i> extract resulted in a dose-dependent and statistically significant reduction of viral load. The extract decreased mRNA levels of Hemagglutin (HA), Neuraminidase (NA) and Matrix protein 2 (M2). Consistently, western blot analysis showed a decrease in major viral proteins HA, Nucleoprotein (NP), Matrix protein 1 (M1) and Polymerase Acidic protein (PA). Confocal images revealed a marked reduction in HA and PA signals, results that are statistically significant according to quantitative fluorescence evaluation. The convergence of results obtained through independent methodologies at both the transcriptional and protein levels highlight the robustness of the findings. These data provide the experimental evidence that <i>Rhus coriaria</i> interferes with influenza A virus replication in airway epithelial cells and support its further investigation as a promising phytochemical platform for the development of novel anti-influenza strategies.